Scrub typhus is a major acute febrile disease in Asia-pacific region caused by Orientia tsutsugamushi. Delays in diagnosis can cause fatal complications, so a rapid and early diagnosis is indispensable for successful treatment. For this reason, a polymerase chain reaction (PCR) based method was developed to detect a specific O. tsutsugamushi gene in a patient`s blood. Real-time PCR has the advantages of high speed, sensitivity, suggesting the utility of this technique for the early diagnosis of scrub typhus.
We evaluated the clinical usefulness of the real-time quantitative polymerase chain reaction (Q-PCR) amplification of 16S ribosomal RNA gene using specially designed primers. We examined blood specimens from 148 adult patients confirmed to have scrub typhus between September 2008 to December 2009. To evaluate the clinical usefulness of 16S rRNA real-time Q PCR, we compared its diagnostic accuracy to that of the following methods: nested PCR targeting the 56-kDa gene, real time Q-PCR targeting the 47-kDa gene, and conventional PCR targeting 16S rRNA gene.
Using O.t-16sRF1 and O.t-16sRR1 primers to amplify the 16S rRNA gene, Q-PCR detected O. tsutsugamushi infection with a sensitivity of 91.9%. C-PCR amplified the 16S rRNA gene, N-PCR targeting the 56-kDa gene, and Q-PCR targeting the 47-kDa gene showed lower sensitivities of 87.8%, 74.3%, and 81.1%, respectively.
16S real-time Q-PCR is clinically useful for rapid diagnosis of scrub typhus and more accurate than 56-kDa N-PCR, 47-kDa Q-PCR, and 16S C-PCR.
N. R. Yun,